In the text below the invention will be referred to as a “sound monitor” in order to differentiate the invention from the common stethoscope.
Definitions used in the text and for the purpose of this invention intended to encompass the following:
“transducer for transforming vibrations to electrical signals”, also called “vibration transducer” e.g. a microphone, a piezoelectric element, and a piezoelectric film.
“transducer for transforming electrical signals to sound” exemplified by e.g. a loud speaker or the equivalent.
“collecting structure” is used for the structure in which the vibration transducer is arranged, e.g. a protruding bell, open-ended, an essentially cylindrical member, or other embodiments describe in the description. The open-ended structure may be closed by a membrane or a cushion, arranged in the structure or at the open end of the same.
The commonly used acoustic stethoscope was invented in 1816 by a Doctor Laennec. The basic design has not been altered since then. The ordinary acoustic stethoscope has a membrane covered chestpiece, which is connected to a flexible tube; this tube is spilt into two parts each having an ear piece. The sound from e.g. a beating heart is captured by the chestpiece and the sound is passed on to the ears of the auscultator, i.e. generally a doctor.
In conventional practice a doctor will apply a stethoscope to a patient and arrive at a conclusion based on the sounds perceived by the doctor. To receive a second opinion, another doctor will have to be able to apply a stethoscope and hear the same sounds. This is a problem—there might not be another doctor present or the other doctor may have hearing problems or frequency response problem.
Another problem occurs in teaching when teaching the student/-s to differentiate between different sounds relating to e.g. the heart cycle only one person can listen at a time. There is no possibility of pointing out a specific sound related to a specific event in the heart.
Inherent problems with the stethoscopes of current acoustic design are thus: Unfavorable design for education, listening in is impossible for simultaneous identification of sounds, abnormalities are hard to detect and impossible to filter. Murmurs are hard to detect without amplification, filtering and isolation.
Listening in during consultation is not easy, and that patients cannot listen in, mystifies the whole process and makes communication and explanations more difficult. With an acoustic stethoscope it is virtually impossible to store sounds for later playback. A microphone and means for treating and storing the sounds are needed to this end.
In the acoustic stethoscope the sound produced by an organ of a living is picked up by a chest piece in the form of pressure waves and from there routed to a flexible acoustic tube, which continues in two acoustic conduits each ending with an ear piece. Acoustic pressure (sound waves) is transported from the chest piece through the conduits to the respective ear piece and will act on the ear to produce sound. The success of the auscultation is thus inherently dependent not only on the stethoscope but also the ears and perception of the auscultator is part of the process. The hearing in different persons naturally differ between the persons and also in the same person the hearing changes with age. Sounds which the young person easily perceives may be totally impossible for the older person to hear.
The traditionally used chest piece has a further drawback in that when the person listening to bodily sounds e.g. the heart sounds he may want to listen at several locations. The reasons may be that the sound is transplanted differently in different directions or when listening to the lungs the doctor listens normally at several quite closely place locations. This means that when the chest piece is moved it is lifted away from the body and put down at a new location. While the chest piece is lifted all sounds from the body are cut off. This gives the doctor several occasions to adjust to listening at every location as the process is broken off when chest piece is lifted.
Medical personnel learn the art of auscultation primarily through the use of an acoustic stethoscope and are trained to hear normal and abnormal heart and lung sounds based on their specific acoustic qualities and the timing relative to other biological sounds.
Electronic stethoscopes with amplification and filtering of sounds are known within the art. In such a stethoscope the sound from biological activity is picked up by a microphone and the signal may be filtered such as to remove noise etc. The filtering is also indicated as being e.g. selective in order to remove signals emanating from another organ than the one which is the focus of the investigation. The signal is thereafter sent to a loud speaker in the conduits of the stethoscope. Such a stethoscope is known from a published US patent application US 2003/0072457 (published Apr. 17, 2004).
Electronic stethoscopes comprising a handheld chest piece communicating with an ear piece or other apparatuses as loudspeakers, recording means etc are also known within the art.
Typically the prior art requires transducers capable of reproducing the full range or close to the full range of sound generated by the body organs. Heart sounds generally lie within the span 17-500 Hz. Key frequencies of interest lie within the span of 17-200 Hz, and some of the more important sounds are found between 17-70 Hz. Small loudspeakers and other transducers have difficulties reproducing this lower frequency range, thus the choice of ear pieces in the prior art is natural.
An object of the invention is an electronic stethoscope, below termed “sound monitor” or “monitor” having improved functionality and design.
A further object of the invention is to provide for an electronic sound monitor which gives the doctor an enhanced and easy to use tool in everyday practice and also during auscultations when there are several listeners.
A further object of the invention is to make possible the use of small loud speakers or other electrical to audio transducers, which are not capable of representing the frequencies generated by the organs of interest. Further objects are solved by the invention through the method devised which involves frequency manipulation of sounds to be reproduced on these devices. This same method has an additional use. In some instances a loud speaker or audio transducer can represent sounds not easily audible by the listener due to limitations of the human in general or a specific defect of the listener's hearing. This method can bring previously inaudible sound into ranges more suitable for the individual.
An example of an organ sound may be heart murmurs. These sounds may occur in addition to normal heart sounds or may even replace aspects of normal heart sounds. To detect or identify these murmurs the sounds are according to the invention altered in aspect so as to intensify the sounds of interest. Organs of the body like the heart have a predictable sequence of sounds. Methods to identify these sequences may include e.g. following selectable options of:                Removal or reduction of known normal sequences of heart sounds or other organs by the mean of analog or digitally analyzing the sound to identify and reduce sections not of interest. This feature in itself is known e.g. through WO02/32313.        Standard automatic volume control in the analog or digital domain normally described as automatic gain control (AGC). The purpose is to maintain a volume level that can be accommodated by the electronic processing methods preventing overload.        Standard filtering techniques like band-pass, hi-pass, and low-pass filters in the analog or digital domain.        Dynamic scaling of sounds in the analog or digital domain, normally described as compression techniques which limits the magnitude of signals to a given range. Lowering the volume of high level sounds and increasing the volume of lower level sounds.        Dynamic scaling of sounds in the analog or digital domain, normally described as expansion techniques which increases the magnitude of signals over a given range. Increasing the volume of higher level sounds in comparison with lower level sounds.        
Further to these methods, which may be used in the monitor according to the invention there will be described below new methods according to the invention regarding the pitch of the sound.
All of the above may be used singly or in combination, selectable by the listener to most effectively target the sounds of interest. Additionally the processing methodology allows automatic adjustments of the parameters that control sound manipulation. This enables the device to maintain the most effective output, tracking changes in the nature of organ sounds.
These and other objects are attained by manipulating the sound such that the frequency is scaled such that the duration and relative sequences of the sound are retained, meaning that the timing of the sounds is correct but the frequency of the sound is different. The final output may not even include frequencies present in the original signal. The effect is that sounds effectively are lifted in pitch facilitating use of small loudspeakers. In fact the organ sounds lowest in pitch, are not possible to be heard even when large loudspeakers are used. When using small loudspeakers in apparatuses according to the art the lower pitched sounds are de facto not represented.